The present invention relates to a method of manufacturing ceramic electronic components such as multilayer ceramic capacitors and the like.
FIG. 7 is a partially cut-away perspective view of a typical multilayer ceramic capacitor comprising a ceramic dielectric layer 1, a conductive layer 2 and a pair of external electrodes 3, in which an end of each respective conductive layer 2 is alternately connected with one of the pair of external electrodes 3 at the two side of the ceramic dielectric layer 1.
Next, a description is given to a method of manufacturing multilayer ceramic capacitors in a prior art.
First, a ceramic sheet eventually constituting the ceramic dielectric layer 1 is prepared by mixing an organic material to a powder mainly composed of barium titanate ,and a metallic paste is applied thereon in a required pattern by a printing method to form the conductive layer 2. Then, a plurality of the ceramic sheets, each applied with the conductive layer 2 thereon, are superimposed one over another in such a way that any two adjoining conductive layers 2 are located opposite to each other with the ceramic sheet sandwiched therebetween, thus obtaining a laminate. The laminate is fired thereafter and a pair of the external electrodes 3 are formed on both side where the conductive layer 2 is exposed.
However, when the porosity of a ceramic sheet is large, the foregoing prior art method allows part of the metallic constituent in the metallic paste to penetrate into the ceramic sheet during the printing process to print directly the metallic paste on the ceramic sheet.
In recent years, a ceramic sheet for a multilayer ceramic capacitor is made thinner and thinner in order to gain higher capacitance in said capacitor, thereby causing a problem of short-circuiting between adjoining two electrodes because of the metal constituent that has penetrated into the ceramic sheet.
The object of the present invention is to provide a method of manufacturing ceramic electronic component with less failures due to said short-circuiting.
In order to solve the aforementioned problems, the method of manufacturing ceramic electronic components according to the present invention is characterized in that the porosity of a ceramic sheet is first reduced and then a conductive layer is formed on the surface thereof, thereby allowing a metallic constituent to be prevented from penetrating into the ceramic sheet with resulting prevention of short-circuiting failure that may otherwise occur between the conductive layers.
A method of manufacturing ceramic electronic components in a first exemplary embodiment of the present invention comprises:
a first step of applying a pressing force to a ceramic sheet containing a ceramic powder and an organic material to have the porosity thereof reduced;
a second step of forming a conductive layer on the ceramic sheet by the use of a metallic paste;
a third step of producing a laminate by stacking a plurality of ceramic sheets, each having the conductive layer formed thereon, in such a way as having the ceramic sheet sandwiched between the adjoining conductive layers located opposite to each other; and
a fourth step of firing the laminate, thus allowing a ceramic electronic component free of short-circuiting failures to be realized.
A method of manufacturing said components in a second exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the porosity of the ceramic sheet before a reduction in porosity after the first step is 50% or more, thereby allowing a ceramic electronic component free of short-circuiting failures to be realized.
A method of manufacturing said components in a third exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the ceramic sheet contains at least a ceramic constituent and polyethylene at the first step, thereby achieving a great effect in reducing short-circuiting failures, because of a high level of porosity in the ceramic sheet containing polyethylene,compared with other organic materials.
A method of manufacturing ceramic electronic components in a fourth exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the porosity of a ceramic sheet at the first step is less than 50%, thereby allowing a metallic constituent to be prevented from penetrating into the ceramic sheet.
A method of manufacturing ceramic electronic components in a fifth exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the pressing force applied to the ceramic sheet at the first step is made less than the pressing force as applied in forming the laminate at the third step, thereby allowing a sufficiently uniform pressing force to be applied to the entire laminate in both areas, with and without a conductive layer at the third step, resulting in a realization of an electronic component that has little structural defect due to failures in adhesion between the ceramic sheets.
A method of manufacturing ceramic electronic components in a sixth exemplary embodiment of the present invention is the method of said components according to the first exemplary embodiment, in which the ceramic sheet is heated while a pressing force being applied thereto at the first step, thereby allowing the fluidity of an organic material to be enhanced by the application of heat with a resulting quick reduction in porosity of the ceramic sheet.
A method of manufacturing ceramic electronic components in a seventh exemplary embodiment of the present invention is the method of said components according to the sixth exemplary embodiment, in which the ceramic sheet is heated at the temperature between the glass transition point and the melting point of at least one organic material contained in the ceramic sheet, thereby allowing the fluidity of organic materials to be enhanced by the application of heat with a resulting quick reduction in porosity of the ceramic sheet.
A method of manufacturing ceramic electronic components in an eighth exemplary embodiment of the present invention comprises:
a first step of applying a pressing force to reduce the porosity in a ceramic sheet comprising a ceramic powder and an organic material;
a second step of forming a conductive layer by a metallic paste on a base film in advance and superimposing the conductive layer on the ceramic sheet;
a third step of producing a laminate by stacking a plurality of the ceramic sheets, each having the conductive layer superimposed thereon, in such a way as having the ceramic sheet sandwiched between the adjoining conductive layers located opposite to each other; and
a fourth step of firing the laminate, thereby allowing a ceramic electronic component free of short-circuiting failures to be realized.
A method of manufacturing ceramic electronic components in a ninth exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, in which the porosity of the ceramic sheet before the first step is 50% or more, thereby allowing a said component free of short-circuiting failures to be realized.
A method of manufacturing ceramic electronic components in a tenth exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, in which the ceramic sheet is prepared so as to contain at least a ceramic powder and polyethylene at the first step, thereby achieving a great effect in reducing short-circuiting failures. The rate of volumetric shrinkage of the ceramic sheet after the application of a pressing force thereto is made uniform in those composition because of the high level in porosity of the ceramic sheet before applying the pressing force thereto and allowing a further reduction in porosity of the ceramic ceramic sheet to be achieved.
A method of manufacturing ceramic electronic components in an eleventh exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, in which the porosity of the ceramic sheet after the first step is less than 50%, thereby allowing the metallic constituent to be prevented from penetrating into the ceramic sheet.
A method of manufacturing ceramic electronic components in a twelfth exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, in which the pressing force applied to the ceramic sheet at the first step is made less than the pressing force as applied in forming the laminate at the third step, thereby allowing a sufficiently uniform pressing force to be applied to the entire laminate in both region with and without the conductive layer at the third step, resulting in a realization of an electronic component that has little structural defect due to failures in adhesion between the ceramic sheets.
A method of manufacturing ceramic electronic components in a thirteenth exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, in which the ceramic sheet is heated while a pressing force being applied thereto at the first step, thereby allowing the fluidity of the organic material to be enhanced by the heat application with a resulting quick reduction in porosity of the ceramic sheet.
A method of manufacturing ceramic electronic components in a fourteenth exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, in which the ceramic sheet is heated at the temperature between the glass transition point and the melting point of at least one organic material contained in the ceramic sheet, thereby allowing the fluidity of organic materials to be enhance by the heat application with a resulting quick reduction in porosity of the ceramic sheet.
A method of manufacturing ceramic electronic components in a fifteenth exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, in which the amount of an organic constituent in the conductive layer before lamination process is from 5 wt % to 15 wt % against 100 wt % of the metallic constituent at the third step, thereby allowing the sufficient adhesion between the conductor and the ceramic sheet to be realized, resulting in obtaining a ceramic component that has little structural defect.
A method of manufacturing ceramic electronic components in a sixteenth exemplary embodiment of the present invention is the method of said components according to the eighth exemplary embodiment, with additional step of applying a pressing force to the conductive layer in the thickness direction thereof placed between the second step and the third step, thereby allowing the microscopic asperities on the surface of the conductor layer to be reduced and contributing further to the prevention of short-circuiting failures.
A method of manufacturing ceramic electronic components in a seventeenth exemplary embodiment of the present invention comprises:
a first step of preparing a laminate by stacking ceramic sheets, each composing an organic material and a ceramic powder and conductive layers one over another alternately; and
a second step of firing the laminate, in which the ceramic sheet is formed with the organic material arranged horizontally in a mesh-like structure and with the organic material and ceramic powder arranged vertically at random, thereby allowing a metallic constituent to be prevented from penetrating the ceramic sheet with a resulting contribution to realizing a ceramic electronic component which is less susceptible to short-circuiting failures.
A method of manufacturing ceramic electronic components in an eighteenth exemplary embodiment is the method according to the seventeenth exemplary embodiment, in which the porosity of the ceramic sheet is less than 50%, thereby allowing a metallic constituent to be prevented from penetrating the ceramic sheet.
A method of manufacturing ceramic electronic components in a nineteenth exemplary embodiment is the method according to the seventeenth exemplary embodiment, in which, after the conductive layer formed on a base film is superimposed on the ceramic sheet at the first step, a step of peeling off the base film and a step of superimposing the ceramic sheet on the conductive layer are repeated one after another, thereby allowing the solvent constituent in the conductive layer to be reduced when compared with the case where the conductive layer is formed directly on the ceramic sheet with a resulting contribution to preventing the metallic constituent from penetrating into the ceramic sheet.
A method of manufacturing ceramic electronic components in a twentieth exemplary embodiment of the present invention is the method according to the nineteenth exemplary embodiment, with an additional step of applying a pressing force to the conductive layer on the base film in the thickness direction before the conductive layer is superimposed on the ceramic sheet, thereby allowing the microscopic asperities on the surface of the conductor layer to be reduced, with a resulting contribution to preventing the metallic constituent from penetrating into the ceramic sheet.
A method of manufacturing ceramic electronic components in a twenty first exemplary embodiment of the present invention is the method of said components according to the seventeenth exemplary embodiment, in which the conductive layer is deposited by the thin film process at the first step, in this case a metallic film is grown into a plate-like shape on the ceramic sheet, thereby allowing the metallic constituent to be prevented from penetrating into the sheet.
A methods of manufacturing ceramic electronic components in a twenty second exemplary embodiment to a twenty fourth exemplary embodiment of the present invention comprise a step of preparing a laminate by stacking ceramic sheets, each containing an organic material and a ceramic powder, and conductive layers one over another alternately, in which the ceramic sheet is formed with the organic material arranged horizontally in a mesh-like structure and arranged at random in the thickness direction, thereby having the particles of the ceramic powder absorbed in the meshes of the organic material. As a result, the ceramic particles are also arranged at random, each presenting a mesh-like structure. Thus, a ceramic electronic component characterized as having a structure formed by stacking the ceramic layers, each having mesh-like structures of ceramic particles arranged at random, and the conductive layers one over another alternately shows a reduced number of short-circuiting pathes.